1. Field of the Invention
The present invention relates to a process and an apparatus for collecting only the filtrate from a slurry of raw pulp and the like, and for measuring pH, conductivity, etc. of the filtrate.
2. Description of the Prior Art
For example, there is known as a filtrate measuring apparatus for collecting a pulp filtrate to measure its pH etc., one as disclosed in a Japanese Utility Model Application under Laid-open No. Hei 6-78844, containing a filtrate sampling pipe connected to a raw-pulp feeding process piping and having a filter attached to the tip of the pipe; a piston disposed to be slidable within the filtrate sampling pipe, which collects a filtrate into the filtrate sampling pipe in a retracting stroke away from the filter and also back-washing the filter in an approaching stroke toward the filter; a detection tank connected via a closing valve to the filter sampling pipe and to which tank the sample filtrate is fed; a detector disposed in this detection tank; and a flush valve which is connected to the filtrate sampling pipe and feeds a wash water through the filtrate collecting pipe and the closing valve to the detection tank.
In the prior art filtrate measuring apparatus described above, only the filtrate is adapted to be collected into the apparatus as the piston slides, so that the apparatus advantageously has a simple structure and can clean fully the inside of the apparatus in a short time. However, since the filter is constantly brought into contact with the slurry fed through the process piping, some kinds of slurry will deposit the the solid content contained in the slurry on the outer side of the filter even if the filter is closed on the inner side by the piston and will cause clogging of the filter. Further, the property of slurry is liable to be changed corresponding to the amount of sample slurry.